Transport characteristics of fragmental polyethylene glycol terephthalate (PET) microplastics in porous media under various chemical conditions

Transport characteristics of fragmental polyethylene glycol terephthalate (PET) microplastics in porous media were elucidated via column experiments under a series combination of electrolytes, pH, and humic acid (HA) conditions. Fragmental PET microplastics showed low mobility in porous media with a small mass recovery rate (<50.1%) even under unfavorable retention conditions. The electrolyte, pH, and HA showed combined impact on PET microplastic transport. PET microplastics mobility was enhanced with decreasing electrolyte concentration, increasing pH, and increasing HA concentration. Basic properties (e.g. destiny and shape) of PET microplastics showed stronger effect on their transport behaviors in porous media rather than the experimental chemical conditions. In general, both environmental factors and basic properties played important roles in controlling the retention and transport of PET microplastics in porous media. A numerical model considering the second order kinetic deposition sites was applied to depict the retention and transport of PET microplastics in porous media. Model simulations well matched the experimental breakthrough curves. Given the fragmental PET microplastics have more realistic and irregular shapes, results from this study can improve present knowledge of the environmental fate and risk of microplastics in underground soil and water systems.